It is well known that certain thermoplastic fibers such as polyester or polyamide (nylon 6 and 66) have both crystalline regions and non-crystalline (amorphus) regions therein. The non-crystalline region has the softening point lower than the melting point of the crystalline region. When the thermoplastic fibers of this nature are heated up to the softening point of the non-crystalline region, the fibers will not lose their integrity as fiber since the crystalline regions yet remain in their original shapes. However, if heated up to or over the melting point of the crystalline regions, the fibers will melt as a whole and lose their original shapes,i.e., will be broken. In the apparel industry, this physical property of the thermoplastic fibers such as polyester and polyamide is advantageously utilized for imparting so-called "permanent press" or permanent pleats to clothing. In addition, this property of the thermoplastic fibers is utilized in the textile industry to set the fabric made of these thermoplastic fibers in a flattened and wrinkle-free condition through heat setting procedure in order to permit following finishing processes to be done easily and adequately on the flattened fabric.
In another aspect, such thermoplastic fabric can be used to form cover materials for foamed plastic articles such as automobile seats, seat cushions, headrests, armrests, or stuffed toys or dolls. In the prior art technique, the cover material can be formed by cutting the fabric into desired shape and size, assembling pieces of cut fabric and sewing the same into a desired contour for a final product to be obtained. These procedures such as cutting, assembling and sewing the fabric to form the cover material capable of covering desired configurations of a final product are rather complicated, cumbersome, time-consuming and hence expensive. From the industrial and commercial view point, it is highly desirable that a method is provided capable of shaping such thermoplastic fabric or film in a flattened condition into desired three dimensional configurations through a single and simple procedure for heating and pressing.
Specifically, a method for fabricating automobile seats or headrests of the prior art comprises laying a cover fabric in a shaping mold having cavity surfaces corresponding to a final product's contour, mating the fabric with the cavity surfaces through vacuuming from the outside, and pouring fluid polyurethane formulations onto the fabric configured as above, and allowing the formulations to foam and expand until it adheres to the inside surface of the fabric. In this method of the prior art, permeable material such as ordinary textile fabric can not be used as cover material because its permeability renders vacuuming procedure inoperable. Such permeable fabric must have impermeable backings applied thereto if employed in the vacuum shaping process. Applying backings to the cover material is, again, cumbersome and expensive operations. Further, final products covered by such impermeable materials are void of comfortableness in use because they can not absorb sweat or other moisture deposited on their surfaces. Moreover, forming the cover material into desired configurations corresponding to the final contours through vacuuming is not so simple and easy that unintended and undesirable malformation may occur in the cover material before pouring polyurethane fluid thereonto causing inferior goods to be produced in many instances.
Apart from vacuum shaping process, a specially designed apparatus having means for heating and pressing the cover material would be required in order to shape the same into desired three dimensional configurations. Such apparatus, however, must be provided individually for different shapes and sizes of the final products and can not be used for manufacturing different products, e.g., automobile seats on one hand, and headrests on the other hand. Individual provisions of shaping apparatus for every different product require excessive investment and is unacceptable to the industry.
Thus, such thermoplastic fabrics as polyester and polyamide, though having good thermal properties as mentioned above, have not fully been developed to their potential abilities such that they can be processed from their flattened states through the single and simple heating and pressing step into desired final configurations, nor a method for performing such process developed.